Stability order of given anion $\mathbf { H C } \equiv \mathbf { C } ^ { - }$ (a) $\mathbf { C H } _ { \mathbf { 2 } } \boldsymbol { = } \mathbf { C H }$ (b) $\mathrm { CH } _ { 3 } - \mathrm { CH } _ { 2 } -$ (c)